In other GM modules like radios ect, when rewriting the VIN, they do not take full affect until doing a proper ignition off/on. On those systems, they do not have a dedicated ignition wire and rely on communication from BCM to tell it to turn off/on. But the VIN in the RAM will be blank, but will not write to memory until full ignition.daniel2345 wrote:Why would key switch undo the changes?
New seed&key is in ram. Key turned, ram written to eeprom. Remember in car, the ecu is not instantly tuned off since it has always battery terminal 30 connected. It switches itself to "sleep" when everything is done.
If you hardcut power on desk, that might not work.
Also the writing of ram to eeprom can be triggered on various events, such as diagnostic writes.
Maybe this is done here.
99% of runtime in lifecycle no such event apart from key cycle occurs.
But remember, im only talking about what might be common.
My eep section has not moved while writing VIN and it has been said it is always on the same position in E38 files?
Edit: wait. I just re read and saw that the "fluctuation" is from 0xC000..0xFFFF. Two sections with 0x2000.
That might be possible, i saw this whole block as eeprom and did not check what is where...
What I was thinking is if RAM is written to memory on every key cycle for the ECU, the RAM contents would overwrite changes made to that section. But It wouldnt make sense that it overwrites that section every time.. it must only occur under specific conditions maybe like you said maybe. But its over two sections so it would make sense it copies from one to the other each time.
